This invention relates to improvements in seating arrangements for poppet or non-return valves.
Many poppet or non-return valves as used hitherto include a dome-shaped head which registers with a correspondingly shaped seat in the valve chamber. In many cases the seating arrangement is metal to metal and because of minor variations between the valve and the seat caused by faulty fitting or wear it has been difficult to obtain a proper seating, consequently such valves leak. This gives rise to constant maintenance problems and renders such valves unsuitable in many applications in particular for high speed cycle operation.
In recent years, attempts have been made to overcome this problem by the use of valves which use an O-ring seating arrangement. The valve has been so constructed that the O-ring is connected to the valve member and seats on a shoulder in the valve chamber. Such valves have not proved entirely satisfactory for high-speed operation. The repeated compression loads on the O-ring causes deformation of the O-ring beyond the elastic limit of the material from which it is made. This has given rise to a breakdown in sealing with the necessity of frequent replacement of the O-ring.
The present invention overcomes the problems associated with the seating arrangements of such valves as encountered hitherto and at the same time provides a valve which is of simple yet robust construction and which can be used for extremely lengthy periods at high speed cycles without breakdown in the valve seating arrangements.